“Why is it so difficult to support Trump without bad-mouthing Cruz?? And vice-versa?”
All Cruz does is bad-mouth Trump. That has been his whole campaign lately.
That is a “Johnny does it” argument. Besides, I see FAAAR more Cruz bashing here than Trump bashing.
I also see Trump bashing Cruz, often. And Trump’s campaign has consisted largely of belittling his opponents.
Your answer still did not explain why you are unable to support your guy without trashing his opponent.